Analysis shows carbon-slashing promise of new biofuel technology

Suleman Din ・ Office of Engineering Communications

Finding an alternative vehicle fuel poses a difficult challenge: it has to be relatively cheap and able to reduce carbon emissions without using up valuable crop land or trees from forests.

Now, researchers at Princeton’s Andlinger Center for Energy and the Environment say one possible solution might be all around us. In a recent paper, the researchers evaluated a method that creates fuel from wood residues, sawdust and branches. The method, called catalytic hydropyrolysis, could use the refining and distribution systems now used for gasoline to create a fuel that would work in modern engines.

Finding an alternative vehicle fuel poses a difficult challenge: it has to be relatively cheap and able to reduce carbon emissions without using up valuable crop land or trees from forests.

Now, researchers at Princeton’s Andlinger Center for Energy and the Environment say one possible solution might be all around us. In a recent paper, the researchers evaluated a method that creates fuel from wood residues, sawdust and branches. The method, called catalytic hydropyrolysis, could use the refining and distribution systems now used for gasoline to create a fuel that would work in modern engines.

“If we want to limit carbon emissions to a safe level, we’re very likely going to have to leave some oil in the ground,” said Eric Larson, a senior research engineer at the Andlinger Center for Energy and the Environment and an author of the paper. “It’s a lot easier if we can find an alternative fuel that we can put into our existing infrastructure.”

In a paper published this spring in the journal Sustainable Energy & Fuels, Larson and Princeton postdoctoral fellow Hans Meerman present designs of processes and comprehensive assessments of fuels production based on catalytic hydropyrolysis, a technique being developed by other researchers. The new technique creates combustible oil by heating biomass in the absence of oxygen. Larson and Meerman designed systems that could create a zero-carbon vehicle fuel, meaning that creating and burning it results in no net emission of carbon. Integrating carbon-capture technology into some of the designs, they found it could actually pull carbon out of the atmosphere while creating fuel.

However, the researchers said there are still questions about whether the technique could scale to an industrial level and about whether it could economically compete with oil. Commercial-scale demonstrations would be needed to answer the question of scale, while the economic question depends on the difficult-to-predict price of crude oil.

Pyrolysis is not a new technology. But Larson said that most pyrolysis techniques create oils that are too acidic and contaminated to be processed in existing crude-oil refineries. Therefore, the researchers concentrated their evaluation on the relatively new technique in which injected hydrogen acts, in the presence of a specialized catalyst, to circumvent the formation of undesirable compounds in the oil product. The addition of hydrogen creates a fuel that will seem relatively familiar to existing refineries, Larson said.